This invention generally relates to electrochemical systems for storage and release of electrical energy. In particular, the present invention relates to electrochemical systems for use in electronic circuits, for example, as capacitors or batteries. More particularly, the present invention relates to electrochemical systems for operation in electronic circuitry, for example, as capacitors or batteries, with either a non-liquid, organic solution, an aqueous solution or a protonic medium electrolyte material positioned between the electrodes.
Further still, the present invention relates to improved designs for bi-polar assemblies that address the deficiencies in existing bi-polar designs. In particular, this invention relates to an assembly of a plurality of single cells of an electrochemical system. More particularly, individual cells may be connected individually to each other to form a stack. Also, stacks may be connected together to form an assembly. Further, the present invention is more versatile for achieving inter-cell or inter-stack connections in series, parallel, or combinations thereof and for achieving hybrid packs of a battery or batteries combined with a capacitor or capacitors in a single package.
As electronic devices and other electrical apparatuses become increasingly more portable and provide more functionality, advances must be made in the components of such devices that enable such portability. As is often the case with current electronics technology, the limiting factor in both size and functionality of an electronic apparatus is the size and weight of its component parts and in particular, the size and weight of its energy storage components. Additionally, the miniaturization of electronics has seen the push towards integrating various components into a single device to save both room and weight within both portable and stationary devices.
The current main energy source used for portable electronics is the electrochemical battery and/or the electrochemical capacitor. One of the limiting features of such current energy storage components is the packaging of the electrochemical system and the interconnection among the cells comprising the system. The current convention is to house the active electrodes and electrolytic material in a metallic casing. This form of housing is available in a wide variety of shapes and sizes. In the past, however, this has lead designers to accommodate the form of the electronic device to the casing rather than adding either the battery or capacitor after designing the device as they choose. As a result, the metal can, as opposed to the functionality of the device, has influenced the design of such portable electronic devices.
Similarly, the ability to enhance voltage and/or current for a given circuit design has required multiple energy storage components within individual cans within the electronic device. Again, this has forced designers to accommodate the design based on the casings needed to house multiple capacitors or batteries.
Alternative packagings for capacitors are known. U.S. Pat. No. 5,591,540, issued to Louie et al., the entirety of which is herein incorporated by reference, discloses an electrochemical charge storage device. While useful for its purpose, the ""540 device, however, provides only a single capacitor cell. With the need for incorporating multiple energy storage components into a single device, using the design of the ""540 packaging simply repeats the space hungry designs of the past.
Further, in most electrochemical systems the electrodes are separated by a liquid solution. In the solution, referred to as an electrolyte, ions can move freely. It is not, however, always convenient to have a liquid present within an electrochemical system. The use of liquids has many disadvantages. First, the liquid may leak from the component. Second, the additional cell elements are required to keep the liquid absorbed between the electrodes. Finally, many of the liquids used are corrosive, caustic, or even flammable.
A liquid electrolyte also has implications for cell design. Typically, liquid electrolyte electrochemical systems are built as individual cells in order to contain the liquid between the electrodes. Since in many applications an operating voltage greater than that capable of being provided by an individual cell is required, a plurality of cells need be connected into a pack to achieve a specified voltage.
U.S. Pat. No. 4,488,203, issued to Muranaka et al., the entirety of which is herein incorporated by reference, discloses an electrochemical double-layer capacitor. While useful for its purpose, the ""203 device discloses only a single capacitive cell xe2x80x9cseparated from one another in a simple manner.xe2x80x9d (See column 2, lines 3-5 of U.S. Pat. No. 4,488,203) Additionally, while capable of being stacked to form a plurality of capacitor cells in series, the ""203 device requires significantly more space and results in additional weight which a truly integrated plurality of capacitor cells within a single component would not.
It is, therefore, desirable to provide an ultra-thin multi-cell energy storage component that may comprise an electrochemical capacitor, a double-layer capacitor or a battery. In an electrochemical capacitor version of the present invention, which may also be referred to as a pseudo-capacitor or batcap, the electrodes comprise material that may participate in reversible charge transfer reactions. Thus, a portion of the energy is stored in the double-layer at the surface of the electrodes and another portion is contributed by the charge transfer reactions. In a double-layer capacitor version of the present invention, essentially all of the energy is stored in the double layer at the surface of the electrodes. In a battery version of the present invention, the anode and cathode materials are specifically chosen so that each reacts during operation of the cell. The chemical energy that is stored in the electrodes is converted to electrical energy via charge transfer reactions of active materials.
It is also desirable to provide a new packaging for an electrochemical multi-cell energy storage component for a single electronic device wherein the cells are in series or parallel or a combination thereof by virtue of the component""s construction in one integrated structure. The packaging material needed for such a method must be a lightweight, flexible material which is inexpensive and can be processed with current processing techniques and tools.
The present invention recognizes and addresses various of the foregoing limitations and drawbacks, and others, concerning both the designs of electrochemical multi-cell energy storage components and methods of making the same. Therefore, the present invention provides an improved ultra-thin electrochemical multi-cell energy storage component comprising electrochemical capacitors, double-layer capacitors or batteries or combinations thereof that are connected in series, parallel or some combination thereof, in addition to an improved method of making the component.
It is, therefor, a principle object of the subject invention to provide an improved electrochemical multi-cell capacitor and/or battery. More particularly, it is an object of the present invention to provide an electrochemical multi-cell capacitor and/or battery within an improved casing. In such context, it is still a more particular object of the present invention to provide an electrochemical multi-cell capacitor and/or battery wherein the improved casing is made of a film material.
Another more particular object of the present invention is to provide an electrochemical multi-cell capacitor and/or battery with a low resistance. In such context, it is a principle object of the present invention to provide an electrochemical multi-cell capacitor with a low equivalent series resistance (hereinafter, ESR) and a high capacity.
It is still a further object of the present invention to provide an ultra-thin electrochemical multi-cell capacitor and/or battery. In such context, it is a more particular object of the present invention to provide an electrochemical multi-cell energy storage component which by virtue of its construction places the multiple connected cells in series, parallel or a combination thereof and allows a single common current collector to form the series connection between two cells or stacks of cells in the same plane.
It is a further object of the present invention to provide an ultra-thin electrochemical energy storage component that is simple and cost-effective to manufacture.
Additional objects and advantages of the invention are set forth herein, or will be apparent to those of ordinary skill in the art from, the detailed description as follows. Also, it should be further appreciated that modifications and variations to the specifically illustrated and discussed features and materials hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitutions of the equivalent steps, means, features, and materials for those shown or discussed, and the functional or positional reversal of various steps, parts, features, or the like.
Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of this invention, may include various combinations or configurations of presently disclosed steps, features, elements, or their equivalents (including combinations of steps, features or configurations thereof not expressly shown in the figures or stated in the detailed description).
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain principles of the invention.
In one exemplary embodiment, there may be provided a multi-cell capacitor that comprises two elements of conductive polymer current collectors coated with a metallic film and adhered to a plastic perforated isolating frame. Such a combination forms a current collector assembly. Within the openings formed in each of the perforated isolating frames is present a high surface area carbon-based electrode material to form capacitive electrode plates. Where a current collector longitudinally electrically connects two iso-planar cells in series, the current collector is referred to as a common current collector. Where a current collector connects only a single cell to some external circuitry or contacts the end cell of a stack of cells, thereby connecting the stack to some external circuitry, the current collector is referred to as a terminal current collector. Such common and terminal current collectors are used externally to the stack or stacks of cells.
A bi-polar current collector assembly, for use internal to a stack of cells connected in series may comprise two plastic perforated isolating frames attached to both sides of a single conductive polymer current collector. The conductive polymer current collector within the bi-polar assembly need not have a metal film coating. On the top and bottom sides of the bi-polar current collector assembly in the openings formed within the perforated isolating frames may be placed the same high surface area carbon-based electrode material to form electrode plates. Such a bi-polar current collector, while primarily used for internal electrical connection within a stack, may also be electrically connected to external circuitry.
The capacitor device may be formed by stacking the external current collector assemblies with the bi-polar current collector assembly or assemblies. On each side of the bi-polar current collector are electrode plates which are separated by proton conductive polymer membranes. The membranes function as a proton conductive layer within each capacitor cell. The capacitor may then be housed within a laminate casing comprising a lightweight flexible non-conductive material, such as polyester coated with a metallic film. The casing may then be hermetically sealed around its periphery to encase the capacitor.
Openings may be left in the periphery for the passage of tab structures. These tab structures may serve as a point for electrical connection between external electronic circuitry and either common current collectors, terminal current collectors, or bi-polar current collectors. The openings may be sealed with a pressure sensitive cold adhesive, thermal adhesive or other type of sealant.
In another exemplary embodiment, the perimeter of the outer casing may be completely hermetically sealed. In the upper surface of the casing may exist two pre-punched holes for electrical connection between the current collector assemblies and the tabs. This places the tabs external to the capacitor device and reduces the occurrence of short circuits and vapor loss and enhances the ease of production and flexibility of tab positioning.